Microbial community composition and metagenomes across the river-to-ocean continuum of the Columbia and Amazon Rivers (Invited)
Abstract
Rivers are the primary conduits for land-to-ocean transfer of materials including terrestrial organic matter, nutrients and anthropogenic pollutants. Microbial communities in rivers, estuaries, and plumes regulate the nutrient concentrations and biogeochemistry of these riverborne materials and mediate their impact on carbon cycling. Despite their importance little is known about the composition and genetic capabilities of these organisms. Here we describe and compare the phylogeny and metagenomic profiles of microbial communities across the river-to-ocean gradients of two very large rivers: the tropical Amazon and temperate Columbia rivers. For the Amazon, samples were collected from the lower 600 km of the river and from surface waters across 1300 km of the plume in 2010 and 2011. For the Columbia, samples were collected along the gradient from river to deep ocean during 14 cruises between 2007 and 2010. Amplicon pyrosequencing of bacterial 16S rRNA genes showed that bacterial communities were similar along the length of the lower Amazon River with variability caused by inputs from major tributaries. Freshwater taxa from both rivers were very rare in plume waters, but in the Columbia River estuary freshwater taxa mixed with marine communities. Communities in both rivers shifted with local seasons, likely due to changes in river environmental conditions including dissolved and particulate organic matter, river flow, and light availability. Seasonal variability was less pronounced in river plumes where spatial variability was greater than temporal variability. Bacterial community composition was very different between the two systems, and was most similar at the marine end of the gradient outside the plumes. Illumina-based metagenomic analyses of a subset of these samples showed similarity in the relative abundance of many annotated gene categories despite differences in phylogeny across salinity gradients. However, several categories of genes varied in relative abundance including genes involved in carbon transformations, revealing distinct patterns in genomic capabilities across the Amazon and Columbia River systems. Together, these phylogenetic and metagenomic data provide insight into the spatial and seasonal succession of microbes and biogeochemical processes associated with riverborne material as it transits from the mountains to the oceans.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMOS51C..06C
- Keywords:
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- 4840 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL Microbiology and microbial ecology;
- 4239 OCEANOGRAPHY: GENERAL Limnology;
- 0428 BIOGEOSCIENCES Carbon cycling;
- 0465 BIOGEOSCIENCES Microbiology: ecology;
- physiology and genomics